1. Field of the Invention
The present invention concerns a new method of manufacturing metal alloys in order to obtain a homogeneous powder of oxides of the metals. The method is more particularly, although not exclusively, related to the manufacture of pellets by cold pressing or by sintering in order to produce semiconductors or superconductors for the manufacture of lightning arresters or voltage limiter components associated with electrical or electronic equipment, for example.
2. Description of the Prior Art
Known components of this kind are usually produced from a powder or granular material comprising an oxide of zinc alloyed with doping elements in the form of oxides of nickel, chromium, manganese, magnesium, bismuth, antimony, silicon, cobalt, and the like.
Conventional methods of using ceramic materials usually consist of weighing the constituent oxides, mixing and grinding them and then making up a mixture in an aqueous medium to obtain a slip. This slip is then sintered at high temperature after pressing to shape as is standard practice in the ceramics art. The component made in this way can have metal current feed electrodes applied to its ends by depositing a metal layer using plasma torch sputtering or any other deposition method. The remainder of the exterior surface is usually coated with various layers of materials providing electrical insulation, physical-chemical and mechanical protection and possibly preventing electrical arcing. In particular, glasses or ceramics compatible with the oxide, synthetic resins such as epoxy resins, silicone products and most known insulating products are used.
Methods of this kind are complex to implement and require large-scale industrial installations including grinders and furnaces. It is also necessary to carry out complex checks on the raw materials to ensure that the final product is of good and reproducible quality. Also, the homogeneity of the product obtained leaves something to be desired because the ground constituents can never be perfectly mixed together.
The improvements which are the subject matter of the present invention are directed to remedying these drawbacks and to providing a method of manufacture which constitutes a better response than hitherto available to the requirements of the art and which in particular produces a homogeneous powder made up of metal alloy oxides.
In a method in accordance with the invention the basic components from which the powder to be made into the semiconductor is obtained are no longer oxides but alloys or mixtures of metals which are subsequently oxidized in the solid, liquid or vapor phase.